Recurrent Colic Diagnosis for Horses

Recurrent colic is typically defined as three or more episodes of transient or prolonged colic occurring over a period of months or upwards of a year. Causes vary and can include parasites, gastric ulcers, sand accumulation, impactions, intermittent intestinal gas, enteroliths (intestinal stones/concretions), intra- or extraluminal masses resulting in partial obstructions, and colonic displacements, among other problems. Although a practitioner cannot always determine a definitive etiology without exploratory surgery, many diagnostics are available to help pinpoint the most likely cause.

A complete history and physical exam with laboratory analysis by a veterinarian is typically recommended for a horse with recurrent colic. The exam should include an oral component, because horses needing dental care might have difficulty chewing and can be predisposed to impactions. Initial evaluation also would include a rectal palpation and might include nasogastric intubation if the horse actively displays colic signs. A complete blood cell count and biochemistry profile evaluates red blood cells, white blood cells, electrolytes, total protein, albumin (a protein manufactured within the liver), and liver and kidney values.

Depending on the geographic region and the veterinary practice, field diagnostic capabilities might be somewhat limited. In these cases a veterinarian likely will recommend fecal sample evaluation for parasites and will discuss deworming program, diet, and how the horse's pasture is managed.

If the initial evaluation doesn't reveal a likely cause for the colic episodes, the veterinarian might consider additional diagnostic testing methods, starting with routinely available procedures such as endoscopy of the stomach or ultrasound of the abdomen. He or she might also recommend an abdominocentesis (a belly tap), radiographs of the abdomen, and small intestinal and/or rectal biopsy. The abdominocentesis, which can be performed under light sedation with a local anesthetic, samples fluid from the abdominal cavity that surrounds the organs and intestine. Inflammation or infection within the abdomen can result in changes in the peritoneal fluid.

Ulcers are a common cause of recurrent colic in performance horses and have been reported in 66-93% of racehorses in training (Murray, 1996; Hammond, 1986; Vatistas, 1999), 67% of endurance horses (Nieto, 2004), and 58% of show horses (McClure, 1999). Horses with equine gastric ulcer syndrome (EGUS) might exhibit poor performance, decreased appetite, weight loss, and recurrent mild to moderate colic. Scoping the esophagus, stomach, and pylorus (the opening from the stomach into the small intestine) in a fasted horse enables a definitive diagnosis of EGUS. Endoscopy also can facilitate small intestinal biopsy of the duodenum (the first part of the small intestine) if an inflammatory process is suspected.

The veterinarian can use ultrasound of the abdominal cavity to evaluate visible portions of the kidneys, liver, spleen, and intestinal tract. Thickening of the intestinal walls can be identified in conditions such as right dorsal colitis and other infiltrative and/or inflammatory intestinal diseases. He or she might also be able to identify abnormal abdominal masses such as an abscess or cancer on ultrasound. Sand can be visualized as well; however, abdominal radiographs are ideal for documenting intestinal sand. Radiographs also are valuable to determine if enteroliths are present.

Despite the aforementioned exams, diagnosis can still be elusive in some recurrent colic cases. With advances in diagnostic techniques and surgical procedures, additional options include standing laparoscopic surgery and abdominal exploratory under general anesthesia. A CT scan and MRI might be available at select referral centers for Miniature Horses, foals, and some ponies. If an abnormality is identified with CT or MRI, surgery might still be required to correct the underlying problem. Fortunately, complications from abdominal surgery have diminished, and success rates have improved considerably. The exact prognosis will depend on the underlying cause.

Horses with recurrent colic can be a significant source of anxiety for owners and veterinarians alike. Thorough evaluation and understanding of possible causes can assist both parties in determining the most likely etiology of the colic. Treatment and management of affected horses are most effective when they can be targeted at a specific established diagnosis.

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